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Stepper Motor controller in development

Discussion in 'Sensors and Actuators' started by Dude22, Mar 30, 2012.

  1. Dude22

    Dude22

    66
    1
    Mar 30, 2012
    Hi everyone,

    My name is Josh and I am working on developing a stepper controller using uln2003a chips. They are currently working great. with only one problem..... the chips have a max of 500 ma. I would like to be able to use MUCH more. I have tried paralleling the chips by stacking them and soldering the corresponding pins together. This was recommended to me my a member on CNCZONE sadly it did not help, the way the chip works (creating a pulse from a steady power supply and a true false signal from the computer) is what I think stops the chips from working paralleled. because the power still went through the same channels at the same amperage and it didn't split itself over both chips. Does anyone have any ideas about how to overcome this???

    Thanks,
    Josh
     
  2. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    read the datasheet, if the chips are able to be paralleled or another way is possible to up the amperage then the datasheet will tell you how to do it.

    I never really looked into this chip, but 500mA to drive a stepper for a cnc is way to small. I have 3 NEMA 17 motors and they need over an amp. So even if you could parallel two chips together, you are still gonna be pushing them very hard.

    What steppers are you trying to drive?
     
  3. GreenGiant

    GreenGiant

    830
    6
    Feb 9, 2012
    did you solder all of the pins together or just the control and output pins?

    if you have the supply pins separate and ONLY the output and control pins connected this should double the output current, though I cant promise anything as Im not familiar with that particular chip.

    why not use some transistors and use the signal from the uln2003a to control them letting a higher voltage/current to be driven that way?
    The timing would not be affected unless you are working with very high speeds, and it should work just as well, without messing with the chip
     
  4. Dude22

    Dude22

    66
    1
    Mar 30, 2012
    I like your idea, but i am a bit stumped with the wiring... would i wire the pulses (at 9 volts and 400 ma) to the base of the transister. The higher voltage and ma power supply (20 volts and 1500 ma) to the transistors collector and then get my higher power pulse out of the emitter??? am I understanding the use of the transistors or am I incorrect???
     
    Last edited: Mar 30, 2012
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,192
    2,694
    Jan 21, 2010
    instead of driving the load through the ULN chips, get a mosfet driver and a suitable mosfet and switching currents of several (to many) amps will be child's play.
     
  6. Dude22

    Dude22

    66
    1
    Mar 30, 2012
    I don't understand... would it be possible to get a wiring diagram???

    here is some more info:

    Put simply, I would like to use the uln2003 to supply motors at above the chips max. how can I do this???
     
    Last edited: Mar 31, 2012
  7. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    why are you so stuck on the uln2003?
     
  8. Dude22

    Dude22

    66
    1
    Mar 30, 2012
    Because it is cheap (23 cents). If you have any other ideas that are around the same cost then i would be open to input.
     
  9. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010

    But it ain't gonna be that cheap if you do something like greengiant said. Every part that you add to the circuit is just gonna up the cost. Probably more so then if you bought a chip that had more current capability from the start.

    You still haven't said what your requirements are. Does this driver need micro-stepping functionality?
     
  10. Dude22

    Dude22

    66
    1
    Mar 30, 2012
    more info.

    I dont really have many requirements, all I need is a 3 axis controller. micro-steping would be nice but is not required. I also need to be able to supply the motors with 24 volts at 1.5 mA. If you have any ideas for the drive that would be cheap the let me know. PS: I am on a tight timeline and need to have the machiene compleated within 1 week!!! :eek::eek::eek::eek:
     
  11. Dude22

    Dude22

    66
    1
    Mar 30, 2012
    I would alos like to add that limet switch capibility would be geat although not nesisary.
     
  12. jackorocko

    jackorocko

    1,284
    1
    Apr 4, 2010
    L298/L297 ~1A can be paralleled
    LMD18245 ~3A can be paralleled

    http://www.divms.uiowa.edu/~jones/step/circuits.html

    limit switches have more to do with the driving software and not so much with the hardware driver of the motor. You reach a limit and the software stops sending signals to the motor driver.
     
    Last edited: Apr 1, 2012
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